Declare intent.
Generate the wiring.

[RpcMethod("clients.get")]
public sealed class GetClient(IAppDbContext db)
  : IHandler<GetClient.Query, Result<Response>> {

  public sealed record Query(Guid Id);
  public sealed record Response(Guid Id, string Name);

  public async ValueTask<Result<Response>> HandleAsync(Query q, CancellationToken ct) {
    var client = await db.Clients
      .Where(c => c.Id == q.Id)
      .Select(c => new Response(c.Id, c.Name))
      .FirstOrDefaultAsync(ct);

    return client is null
      ? AppError.NotFound($"Client {q.Id} not found.")
      : client;
  }
}